sys/sysctl.h: Fix wrong assertion with multiple access flags

With multiple flags passed in, e.g., CTLFLAG_RD | CTLFLAG_CAPRD, due to
the precedence rules, this will result in false positive assertion. Fix
that by surrounding the replacement lists with parentheses.

Reviewed by:	imp, erj
Fixes:		10a1e98 iflib: mark isc_driver_version as constant
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D45531

sys/sys/sysctl.h

@@ -403,14 +403,14 @@ TAILQ_HEAD(sysctl_ctx_list, sysctl_ctx_entry);
 #define	SYSCTL_CONST_STRING(parent, nbr, name, access, arg, descr)	\
 	SYSCTL_OID(parent, nbr, name, CTLTYPE_STRING | CTLFLAG_MPSAFE | (access),\
 	    __DECONST(char *, arg), 0, sysctl_handle_string, "A", descr); \
-	CTASSERT(!(access & CTLFLAG_WR));				\
+	CTASSERT(!((access) & CTLFLAG_WR));				\
 	CTASSERT(((access) & CTLTYPE) == 0 ||				\
 	    ((access) & SYSCTL_CT_ASSERT_MASK) == CTLTYPE_STRING)
 
 #define	SYSCTL_ADD_CONST_STRING(ctx, parent, nbr, name, access, arg, descr) \
 ({									\
 	char *__arg = __DECONST(char *, arg);				\
-	CTASSERT(!(access & CTLFLAG_WR));				\
+	CTASSERT(!((access) & CTLFLAG_WR));				\
 	CTASSERT(((access) & CTLTYPE) == 0 ||				\
 	    ((access) & SYSCTL_CT_ASSERT_MASK) == CTLTYPE_STRING);	\
 	sysctl_add_oid(ctx, parent, nbr, name, CTLTYPE_STRING | 	\